Such a switch strip comprises an inner electrode, an outer electrode and a space. The outer electrode surrounds the inner electrode more or less concentrically at a distance. The space between the outer electrode and the inner electrode is insulating and dielectric. The outer electrode is deformable by a force applied from the outside. The deformation of the outer electrode is able at least in portions to bring the inner electrode and the outer electrode into contact with each other.
Such a switch strip is used in closure elements of automotive vehicles, for example in the area of an electrically driven sliding door or with electrically driven windows and flaps, such as trunk lids and doors, as well as sliding sunroofs. The switch strip is part of a safety device to prevent objects or limbs being trapped during the closure operation of the closure element. The switch strip can of course also be used with other electrically driven closure elements, such as windows or doors.
Anti-trap protection systems using such switch strips are basically differentiated into tactile and capacitive anti-trap protection systems. With tactile anti-trap protection systems, deformation of the switch strip is necessary to such an extent that two electrodes come into contact with each other. This necessitates a certain compressive force on the switch strip which can be a drawback in the case of limbs being trapped. Irrespective of this drawback, anti-trap protection systems are equipped with switch strips which also enable a tactile switching function, to ensure, for example, the function of the anti-trap protection when the capacitive switching function fails. In this way the trapping of objects, such as wood or plastic, which cause a non-detectable change in the capacitance of the switch strip, can also be prevented.
On the other hand, capacitive anti-trap protection systems have the advantage that they detect an obstruction as soon as the capacitance of the switch strip is changed. A change in capacitance can occur first when a limb, for example, approaches the switch strip. If for some reason the obstruction is not detected, a further change in capacitance can occur by the deformation of the switch strip. If a switching event is not triggered even at this stage, mutual contacting of the electrodes, at the latest, will trigger a switching event. The switch strip and thus the anti-trap protection system are doubly protected.
Such a switch strip is known from DE 10 2005 028 739 B3. The switch strip disclosed in this reference, comprises an elastically deformable hollow profile body, comprising an inner surface surrounding a cavity. The inner surface includes at least two spaced, electrically conductive contact portions. The contact portions furthermore include one or more switching protrusions.
DE 10 2008 050 897 A1 discloses a profile for sensors for the capacitive detection of obstructions. The profile includes two conductors extending in parallel to the longitudinal direction of the profile and spaced from each other, and is characterized in that at least one third conductor is provided within the profile spaced from the first conductor in the detection direction.
A drawback of this profile is that there is at least one direction in which the detection of obstructions is not as good as in other directions. The orientation thus has to be taken into consideration during installation of the switch strip, which makes the installation cumbersome and expensive.
A further anti-trap protection is known from EP 1 154 110 B2, which comprises a capacitive switch strip. An obstruction is directly detected by means of an electric field, which extends in the scanning range.
A drawback of this switch strip is that certain obstructions, such as wood or plastic, are only poorly detected or not at all.
Further tactile switch strips are known from US 2004/0107640 A1 and DE 10 2011 077 014 A1. These switch strips also have a preferred direction of deformation.
It is thus the object of the present invention to provide an easily manufacturable switch strip, which works irrespective of a particular rotation with respect to the longitudinal axis.